Nocturnal Behavior of Breeding Trumpeter Swans

October1994] ShortCommunications andCommentaries 1013

uador. Ph.D. dissertation, Louisiana State Univ., Y•-•-•GUT•, S. 1958. Systema Helminthum. I. The Baton Rouge. digenetic trematodesof vertebrates.Interscience TRAvASSOS,L. 1944. Revisao da familia Dicrocoeli- Publishers, New York. idae Odhner, 1910. Monogr. Inst. Oswaldo Cruz Rio 2:1-357. ReceivedI December1993, accepted 10 February1994. TRAVASSOS,L., J. F. T. FREITAS,AND A. KOHN. 1969. Trematodeos do Brasil. Mere. Inst. Oswaldo Cruz Rio 67:1-886.

The Auk 111(4):1013-1018, 1994

Nocturnal Behaviorof BreedingTrumpeter Swans

PAUL HENSON• AND JAMESA. COOPER Departmentof Fisheriesand Wildlife, University of Minnesota,St. Paul,Minnesota 55108, USA

The study of nocturnal waterfowl behavior has re- Nocturnal feeding and other behaviors have been ceivedlittle attention,in part becauseresearchers have documentedin wintering Mute Swans(Cygnus olor), usually assumednight to be a time of little or no Bewick's Swans (C. columbianusbewickii), and Trum- activity (Baldassarreet al. 1988, Jordeand Owen 1988, peter Swans (C. buccinator;Owen and Cadbury 1975, Paulus 1988). The few studies that have focused on McKelvey and Verbeek 1988). Nocturnal behavior of nocturnalactivity have shown a surprisingamount breeding swans is unknown. Cooper (1979) and of behavioral variation (Linsell 1969, Nilsson 1970, Hampton (1981) used electronicmonitoring devices Swansonand Sargeant1972, Ydenberg et al. 1984). (Cooperand Afton 1981)to quantifythe presenceof Waterfowlstudies that includedevaluations of night- incubatingfemale Trumpeter Swans at the nest dur- time activity have revealeda variety of nocturnalbe- ing the nocturnalperiod, but nighttime behaviorof haviors(Raveling et al. 1972,Ebbinge et al. 1975,Tam- males,nonincubating females, and cygnetswas not isier 1976, Pedroli 1982,Aldrich and Raveling 1983, evaluated. Moulton and Weller 1984, Paulus 1984, Madsen et al. We studied the nocturnal behavior of Trumpeter 1989).However, none of thesestudies focused spe- Swansbreeding in Wyoming and Idaho in 1991.Our cifically on nocturnal behavior. objectivewas to quantify nocturnalbehavior of breed- Differences in nocturnal behavior between water- ing Trumpeter Swansthrough direct observationsus- fowl maybe dueto the greatvariety of environmental ing night-vision equipment. Specificquestions ad- and physiologicalstimuli encounteredby various dressedwere: (1) Are breeding swansactive at night? species (Jorde and Owen 1988). Nilsson (1970), for (2) If nocturnal activity is occurring, is it correlated example,found that three of nine speciesof diving with environmental and physiological factors?(3) ducksstudied in Swedenwere predominantlynoc- What is the relative importanceof diurnal and nocturnal feeders, while the other six were diurnal; nocturnal periods to breeding swans? turnal feedersmostly fed on sessilefoods while the Methods.--Stagingand breeding swans were ob- diurnalbirds ate moremobile prey. Predationpres- servedon wetlands in: Wyoming at YellowstoneNa- sureis lessintense at night and may encouragenoc- tional Park; Idaho in the Ashton and Island Park Dis- turnal feeding in someducks (Tamisier 1974, Paulus tricts of the Targhee National Forest, in Harriman 1984).Nocturnal feeding also might be importantto State Park, and on the Sand Creek State Wildlife Ref- birdsthat areenergetically stressed, such as prelaying uge. The ecologicalaspects of this region have been femalesor birds undergoingwing molt (Jordeand describedby Banko(1960), Shea (1979), and Maj (1983). Owen1988). These examples illustrate the importance Observation blinds were erected at staging areas of includingnocturnal observations when studying and on nearby hills that overlookedfour swan breed- a species'behavior and ecology. Conclusionsbased ing territories.All blinds were hidden by vegetation solelyon diurnaldata will not representdiel patterns and were located 100 to 250 m from the nest mounds. and might lead to a misinterpretationof diurnal ac- Observationsalso were recordedfrom vehiclesparked tivities (Baldassarreet al. 1988,Jorde and Owen 1988). on roads overlooking two other territories. We observed each territory every two to four days from prelaying through brood rearing. We used spotting • Present address:U.S. Fish and Wildlife Service, scopes(60 x ) by day and Noctron-V Model 9878 light- Portland Field Station, 2600 S.E. 98th Avenue, Suite intensifyingnight-vision scopes (Varo Inc., Electron 100, Portland, Oregon 97266, USA. Devices Division, Garland, Texas) at night. Night- 1014 ShortCommunications andCommentaries [Auk,Vol. 111

TABLE1. Mean activity time budgets (in percent) equally distributed among swan territories, values during diurnal and nocturnal observationperiods were calculatedfor individual birdsby averagingthe for nonbreedingTrumpeter Swans in Wyomingand daily meansfor each period of the breeding season Idaho, 1991 (two-tailed unpaired t-test, df = 27). (i.e.prelaying/laying, incubation, posthatching). Thus, every bird contributed one mean diurnal value and Behavior Daya Nightb P one mean nocturnal value for each statistical test. Mean Head-up 17.9 16.8 0.291 time-budget data were transformedwith an arcsine Feeding 48.0 21.4 0.003 calculation(Zar 1984). Two-tailed paired t-tests (un- Preen 30.3 13.7 0.123 less otherwise noted in text) were used to evaluate Sleep 3.8 48.1 0.0005 differences between diurnal and nocturnal behaviors, • 17 birds, 6 days,313 scans. ambient temperatures,frequency of agonisticinter- b 12 birds, 3 nights, 160 scans. actions,types of foraging,and lengthof feedingbouts. Results.--Observationsbegan on 17 April 1991and visionscopes were equipped with 135-mmfl.8 lenses ended27 July 1991.Swans were scanned7,791 times that provided just under 3 x magnification,but op- during 824 h of observationat six breeding territories timal light conditionsallowed us to substitute100- and two staging areas.There were 72 nocturnal ob- 300-mm and 600-mm lenses that provided 6x and servation sessions(n = 3,963 scans)and 75 diurnal 12 x magnification,respectively. No additional light sessions(n = 3,828 scans).Most diurnal and nocturnal sources were used to illuminate and monitor birds, observationperiods lasted at least 3 h, and over half except that on occasiona penlight with a red filter of the nocturnal sessions extended from sunset to was usedto initially locatebirds on wetlands. sunrisewhen two observerswere available. Length Observation periods were not random due to lo- of the nocturnal period decreasedfrom about 9 h in gistical and accessconstraints. Nocturnal observa- late April to about 7 h during midsummer.Daytime tions were made under clear to cloudyskies because observationtemperatures at all six territories (• = 12.8 night-vision scopesdo not function well in the rain + 1.68øC)were warmer than nocturnal temperatures (Paulus1984). Optimal conditionsoccurred under clear (œ= 4.6 + 1.33øC,t = 6.62, df = 5, P = 0.001).A daily skieswith some moonlight and, at such times, obser- rangeof 20øCbetween the high and low temperatures vation quality approachedthat of diurnal sessions. was common,and the lowest nocturnal temperature During the worst nocturnal conditions, incubating during observationswas -6øC. femalescould only be recordedas on or off the nest; Twenty-nine swanswere monitored during six di- males could not be seen and were recorded as un- urnal and three nocturnal observation sessions before known. the spring thaw of breeding areas.Flocks of 100 to Swan behavior was recordedusing NEC-8300 por- 150 birds congregatedat staging areas,where birds table laptop computers.Birds were sexedby observ- slept,fed, preened,swam, walked, flew, and engaged ing copulation and egg-laying behaviors, and indi- in agonisticbehavior both day and night (Table 1). vidualswere recognizedby noting the uniquefeather Sex and breeding statusof staging swans were un- stainpatterns on the head and neckof eachbird (Coo- known, but all were probablynonbreeding birds be- per 1979,Hawkins 1986).Scan observations (Altmann causebreeders had left staging areas and were de- 1974) of swan locations and behaviors were recorded fending territories.Twelve of the 29 birds had gray at 6-min intervals. Previous research found no dif- plumageand were hatchedthe previousyear, and all ference in Trumpeter Swan time budgetsusing both birds fed in groups of three or more. None was ob- 2-min and 6-min intervals (Grant 1991).Terminology viously paired. describing incubation recesses,behaviors, and pos- Trumpeter Swanson breeding territories exhibited tures was adapted from Lazarus and Inglis (1978), a range of nocturnalactivities throughout the season. Cooper (1979), and Hawkins (1986). Behavior cate- Male swans (n = 6) were active for all or part of 53 gories included feeding, head up (alert), preening, of 60 (88.3%)nocturnal observationperiods and were nestbuilding, courtship,agonistic interaction, sleep- not observedduring the nine remaining sessions.Fe- ing or resting,incubation, brooding, and other/un- males(n = 6) were activeduring 34 of 68 (50%)periods known. Birds sleeping/resting or incubating were and were not observedduring one session.Swan pairs considered inactive; all other behaviors were consid- hatchedcygnets on four of the six nestingterritories, ered active. Continuous observations (Altmann 1974) and cygnetswere active on 10 of 19 (52.6%) nights. were used to record feeding-bout length and re- One pair did not initiate incubationand may not have sponsesof swansto predatorsand conspecifics;activ- laid, while another pair laid and incubated eggsbut ities were timed by stopwatchand describedinto a no eggshatched successfully. tape recorder. Time budgets for adult swans were divided into A single estimate of activity for each diurnal or prelaying/laying, incubation, and posthatchingpe- nocturnal observationperiod was calculatedas the riods.Feeding was the predominantdiurnal and noc- percentageof scansspent in each behavior during turnal behavior of female and male swans during that observationperiod. Becausesampling was un- prelaying(Table 2). Incubatingfemales fed little dur- October1994] ShortCommunications andCommentaries 1015 ingthe day and never at night. None of the five incubatingfemales left their nestsduring 33 nocturnal observationsessions, while diurnal feedingre- cesseswererelatively common. Maleswans reduced theirfeeding rate during incubation and fed lessat nightthan by day (Table 2). Males often were difficult to observewhen inactiveduring the incubationand posthatchingperiods, which resultedin a relatively largepercentage of unknownobservations for these III birds(Table 2). Adults of both sexes increased overall feedingactivity after the cygnetshatched. Most feed- ingtook place by day, while sleeping and brooding (femaleonly) were most common atnight. Cygnetsfed predominantlyduring the diurnal pe- III riod (Table 2), but three of the four broods also fed regularlyatnight. Cygnets less than two weeks old spentan averageof 2.1 + 1.2%of their timefeeding at night,while those from two to five weeks old spent 16.1+ 6.0%of their time feeding atnight (t = -2.82, .t df= 3,P = 0.067).Diurnal feeding activity for cygnets undertwo weeks averaged 34.2+ 6.0%,while those fromtwo to fiveweeks old averaged 48.9 _+ 4.3% (t = -1.24,df = 3,P = 0.32).Lengths ofmale diurnal andnocturnal feeding bouts did notdiffer (diurnal, • = 43.0_+ 5.57 rain, n = 78;nocturnal, • = 51.9 _+ 8.88rain, n = 47;t = - 1.24,df = 3, P = 0.30),nor did femalebouts (diurnal, • = 50.0 + 5.84 rain, n = 54; nocturnal,• = 49.6+ 8.96rain, n = 36;t = 0.05,df = 3,P = 0.96).However, cygnet diurnal feeding bouts were almosttwice as long asnocturnal bouts (diurnal, • = 57.5+ 7.12rain, n = 23;nocturnal, œ= 30.3+ 6.17rain, n = 11;t = 5.52,df = 2, P = 0.031).Swans fedat, above, or belowthe water surface, and there were no differences between the diurnal and noctur- nalperiods inrelative types offeeding behavior for males,females, or cygnets(all P > 0.112). Adultswans displayed aggressively towardother swansand waterfowl (n = 58),especially Canada Geese (Brantacanadensis, n = 33). There was no difference in frequencyof agonisticinteractions between day and nightperiods. Nesting swan pairs averaged 6.8+ 3.3 diurnalagonistic encounters and5.0 + 1.7nocturnal encounters(t = 0.772, df = 4, P = 0.483). Males reg- ularlychased other swans and geese at night,and swanscalled through the night on several territories. Swanswere observed atnight in triumphdisplays (n = 4) aftersuccessful territorial defense encounters with otherswans (see Cooper 1979). Ducks were chased on only threeoccasions and were usually tolerated bythe swans. Feeding swans were regularly accom- paniedat nightby smallnumbers of AmericanWi- geons(Mareca americana), Mallards (Arias platyrhyn- chos),Ring-necked Ducks (Aythya collaris), or Amer- icanCoots (Fulica americana). Ducks fed less common- lynear swans that had cygnets, butthese observations were not quantified.Swan copulationswere seendur- ingthe day (n= 5), but no copulations orother court- shipbehaviors were seen at night.Courtship and ag- onisticbehaviors comprised a relatively small per- ShortCommunications and Commentaries [Auk, Vol. 111 centageof the time budget and are included in Table nantsof Trumpeter Swan breeding behavior(Henson 2 within the "other/unknown" category. and Cooper 1993).Cooper (1979) proposedthat cap- Potential predatorsof eggs,cygnets, or adult trum- tive Trumpeter Swans are relatively independent of peters were rarely seen at night. Coyotes (Canisla- short-termweather variationsduring incubation due trans)were heard calling every evening near all ter- to their considerablebody size and large eggs that ritories, but were seenon only four occasions.A rac- cool slowly. However, wild Trumpeter Swan females coon(Procyon lotor) and a striped skunk (Mephitisrne- in Alaska initiated significantly fewer incubation re- phitis)each were observedonce at night. The adult cessesearly in the morning and late in the evening swanswere aware of the presenceof these animals, when temperatureswere coolest,and the early and exhibiting alert posturesand calling during two of late recesseswere shorterthan midday recesses(Hen- the coyoteencounters. During the raccoonencounter, son and Cooper 1993). These females also initiated the adults led their cygnetsaway from the shore to fewer recessesin rainy weather than in clear or over- the center of the wetland. River otters (Lutra cana- castweather. Female swans,like many other water- densis)were seen on two territories during the day, fowl, seem sensitive to environmental variables and but not at night. minimize the cost of recessesby taking them in the Discussion.--Night-visionscopes intensify available warmest or driest parts of the day (see Afton and light, and birds that reflect more light are easier to Paulus 1992). Hawkins (1986) documented similar observe.Large white swanswere more obviousthan patterns in Tundra Swans (Cygnuscolumbianus col- darker-coloredbirds suchas geese and ducks,but the umbianus)nesting in Alaska. latter were always viewable during averageobser- The Idaho-Wyomingstudy areais locatedat greater vationconditions. The mostimportant feature of nightthan 2,000m in elevation,and nocturnaltemperatures vision equipmentis that it allows for direct, contin- were regularly below or near freezing during most uousobservations. Indirect or discontinuoussystems, of the incubation period. Trumpeter Swans in our such as electronic-monitoringdevices or time-lapse study may avoid nocturnal recessesbecause the costs cameras,are subjectto malfunction and may lead to to eggschilled by nighttime temperaturesexceed en- a misinterpretation of data. For example, Hampton ergeticgains. Egg chilling, while not necessarilyfatal (1981) used an electronic multiple-sensor system to the embryos,could lengthen the incubationperiod (Cooper and Afton 1981) to monitor nesting Trum- and lower productivity(see Skutch 1976:202, Aldrich peter Swansin Idaho and concludedthat incubating and Raveling 1983). Northern-breedingswans might females took regular nightly recesses.We question have evolved higher rates of incubation constancy the resultsof his study becauseincubation rhythms than temperate-breedingswans so asto minimize the in his data are consistent with inaccuracies associated length of the incubationperiod in areaswith shorter with battery drawdown in the monitoring system breedingseasons (Kear 1972). (Cooper and Afton 1981), and becausenocturnal be- It is not known whether cygnetswere directly in- havior was not directly observedand verified. fluencedby nocturnaltemperatures or if diet differ- Our resultsdemonstrate that stagingand breeding encesin cygnetbehavior were due to issuesrelated Trumpeter Swansare active at night to varying de- to age,such as foragingability or experienceor other grees depending on the period of the breeding sea- environmental factors such as food availability (see son. The nocturnalperiod is as important as the di- Hensonand Cooper1993). Cygnets were broodedby urnal period to pretaying/laying femalesbecause in- femalesfor longer periods at night, and cygnet noc- dividualbirds spend considerably more time foraging turnal feedingbouts were shorterthan diurnal bouts. than during the incubationand posthatchingperiods. Possibly,younger cygnetsfed lessat night than did Female geeseand swans forage intensively during older cygnets,but we were unable to detect feeding the pretayingphase of reproductionin orderto build differencesin our smallsample. Owen and Kear (1972) up nutrient and energy reservesfor laying and in- proposedthat youngcygnets rely on visualcues for cubation (Ryder 1970, Owen and Kear 1972, Inglis food selectionin the daysimmediately after hatching, 1977, Fox and Madsen 1981, Bromley 1984, Gauthier while older cygnetsprobably use touch to locatefood and Tardif 1991).Trumpeter Swan femalesin Alaska items. follow this pattern (Grant 1991).During the incuba- Predatorsprobably are lessimportant than ambient tion and posthatchingperiods, swans greatly cur- temperaturein influencing nocturnal behavior of tailed nocturnal foraging, probably to prevent egg Trumpeter Swans.The large body size and protective coolingduring the lower nighttimetemperatures and behaviorof adult swansdiscourages most avian and perhapsto discourageegg and cygnetpredation. Fe- smallmammalian predators (Banko 1960, Henson and male geeseremain on the nest at night for the same Grant 1992).Incubating females never took nocturnal reasons, even though the birds are energetically feedingrecesses even though males were nearbyand stressed(Aldrich and Raveling 1983,Thompson and were availableto defend eggsas they do during di- Raveling 1987, Madsen et at. 1989). urnal recesses(Henson and Grant 1991, Henson and Availability and quality of food resourceson the Cooper1992). We rarely observednocturnal preda- breeding grounds are probably important determi- tots active near swan territories.Coyote predation on October1994] ShortCommunications andCommentaries 1017 nestingTrumpeter Swans has occurredin the study habits, and population in the United States.U.S. area(T. McEneaney,Yellowstone National Park,pers. Fish Wildl. Ser., N. Am. Fauna 63. comm.),but island-nestingswans are lessvulnerable BROMLEY,R. G. 1984. The energetics of migration to terrestrial predators than are geeseand upland- and reproductionof DuskyCanada Geese (Branta nestingswans and ducks(Owen and Cadbury 1975, canadensisoccidentalis). Ph.D. dissertation,Oregon Henson and Grant 1992).In addition, potential avian State Univ., Corvallis. predators such as corvids and non-ow! raptors are COOPER,J.A. 1979. Trumpeter Swan nesting behav- mostly diurnal. ior. Wildfowl 30:55-71. Our research demonstrates that behavioral studies COOPER,J. A., AND A.D. AFrON. 1981. A multiple of swans(and perhapsmost other large birds) should sensorsystem for monitoring avian nestingbe- includea studyof nocturnalactivities whenever pos- havior. Wilson Bull. 93:325-333. sible. Nocturnal behavior patterns observedduring EnnINGE, B., K. CANTERS,A•D R. DRENT. 1975. For- our study were unexpectedand provide evidence to aging routines and estimated daily food intake better interpret diurnal swan behavior and energet- in Barnacle Geese wintering in the northern ics. Our resultssuggest that environmental variables Netherlands. Wildfowl 26:5-19. influencenocturnal behavior. However, a larger sam- Fox, A.D., AND J. MADSEN. 1981. The pre-nesting ple of individual adult birds is needed to demonstrate behaviour of the Green!and Whitefronted Goose. a convincing relationship between ambient temper- Wildfowl 32:48-54. ature and behavior patterns. GAUTHIER,G., AND J. TARDIF. 1991. Female feeding Acknowledgments.--Fundingand materials for this and male vigilance during nesting in Greater studywere providedby the Universityof Minnesota, Snow Geese. Condor 93:701-711. the U.S.D.A. Forest Service, Targhee National Forest, GP,A•T, T.A. 1991. Foraging eco!ogyof Trumpeter Ashton and Is!and Park RangerDistricts, the Dayton- Swansbreeding on the Copper River De!ta, Alas- Wilkie Natural History Fund of the Bell Museum of ka. M.S. thesis, Univ. Minnesota, St. Paul. Natural History at the University of Minnesota, W. HAMPTON,P. D. 1981. The wintering and nesting H. and P. A. Henson, the Minnesota Waterfow! As- behavior of the Trumpeter Swan. M.S. thesis, sociation,Pittsburgh Plate Glass,Inc., The Trumpeter Univ. Montana, Missoula. SwanSociety, and the U.S. National Park Service(Yel- HAWKINS,L. 1986. Nesting behaviour of male and lowstoneNational Park). Field assistancewas provid- femaleWhistling Swansand implicationsof male ed by E. Scott,J. Shippee,J. S. Coogan,J. Novick, and incubation. Wildfowl 37:5-27. B. Vinnedge. We owe specialthanks to G. M. Worden, HENSON, P., AND T. A. GRAhrr. 1991. The effects of T. S. Gelatt, J. D. Kelley, D. Strickland,A. L. Wilson, humandisturbance on TrumpeterSwan breeding D. As!ett, E. E. Eyraud,and T. McEneaney.A. Powe!!, behavior. Wildl. Soc. Bull. 19:248-257. M. G. Gulick, T. A. Grant, T. S. Gelatt, F. McKinney, HENSON, P., AND T. A. GRANT. 1992. Brown bear, J.P. Savard,D. G. Jorde,R. G. Brom!ey,and an anon- Ursusarctos middendorffi, predation on a Trum- ymousreviewer commentedon the manuscript.C. M. peter Swan, Cygnusbuccinator, nest. Can. Field- Baggotgenerously provided coffeefor nocturnalob- Nat. 106:128-130. servatiorts. HENSON, P., AND J. A. COOPER. 1992. Division of labour in breeding Trumpeter SwansCygnus buc- LITERATURE CITED cinator. Wildfowl 43:40-48. HENSON,P., ANDJ. A. COOPER.1993. Trumpeter Swan A•rON, A.D., AND S. L. PAUI•US. 1992. Incubation incubationin areasof differing food quality. J. andbrood care. Pages 62-108 in Eco!ogyand man- Wildl. Manage. 57:709-716. agement of breeding waterfowl (B. D. J. Batt, A. INGI•IS,I. R. 1977. The breeding behaviour of the D. Afton, M. G. Anderson,C. D. Ankney, D. H. Pink-footed Goose: Behavioural correlates of Johnson,J. A. Kad!ec, and G. L. Krapu, Eds.). nesting success.Anim. Behav. 25:747-764. Univ. Minnesota Press,Minneapolis. JORE)E,D. G., AND R. B. OWEN. 1988. The need for ALDPaCH, T. W., AND D. G. RAVELING. 1983. Effects nocturnalactivity and energy budgetsof water- of experienceand body weight on incubation fowl. Pages169-180 in Waterfowl in winter (M. behavior of Canada Geese. Auk 100:670-679. W. Weller, Ed.). Univ. Minnesota Press, Minne- ALTMANN,J. 1974. Observational study of behav- apolis. iour: Sampling methods.Behaviour 49:227-267. KEAR,J. 1972. Reproductionand family life. Pages BALDASSARRE,G. A., S. L. PAULUS, A. TAMISIER, AND R. 79-124 in The swans (P. Scott, Ed.). Houghton D. TITMA•. 1988. Workshopsummary: Tech- Mifflin Co., Boston. niques for timing activity of wintering water- LAZARUS,J., AND I. R. INGI•IS. 1978. The breeding fowl. Pages 181-190 in Waterfowl in winter (M. behaviour of the Pink-footed Goose: Parental care W. Weller, Ed.). Univ. Minnesota Press, Minne- and vigilant behaviour during the fledging pe- apolis. riod. Behaviour 65:62-88. BANKO,W.E. 1960. The TrumpeterSwan: Its history, LINSEU•, S.E. 1969. Pre-dusk and nocturnal behav- 1018 ShortCommunications andCommentaries [Auk,Vol. 111

iour of Goldeneye, with notes on population Ducks on Swisslakes during winter. Wildfowl composition.Wildfowl 20:75-77. 33:105-112. MADSEN, J., T. BREGNBALLE,AND F. MEHLUM. 1989. RAVELING,D., W. E. CREWS,AND W. D. KLIMSTRA. 1972. Study of the breeding ecologyand behaviour of Activity patternsof CanadaGeese during winter. the Svalbard population of Light-bellied Brent Wilson Bull. 84:278-295. Goose Branta bernicla hrota. Polar Res. 7:1=21. RYDER,J.P. 1970. A possiblefactor in the evolution MALM. B. 1983. AnalysisofTrumpeterSwanhabitat of clutch size in Ross' Goose. Wilson Bull. 82:5- on the TargheeNational Forestof Idaho and Wy- 13. oming. M.S. thesis,Montana StateUniv., Boze- SHEA,R.E. 1979. The ecologyof the TrumpeterSwan man. in YellowstoneNational Park and vicinity. M.S. McKELvE¾, R. W., AND N. A. VERBEEK. 1988. Habitat thesis, Univ. Montana, Missoula. use, behaviour, and managementof Trumpeter S•ctrrcH,A. F. 1976. Parent birds and their young. Swans, Cygnusbuccinator, wintering at Comox, Univ. Texas Press, Austin. British Columbia. Can. Field-Nat. 102:434-441. SWANSON,G. A., AND A. B. SARGEANT.1972. Obser- MOULTON,D. W., AND M. W. WELLER.1984. Biology vation of nighttime feeding behavior of ducks. and conservation of the Laysan Duck (Anaslay- J. Wildl. Manage. 36:959-961. sanensis).Condor 86:105-117. TAMISIER,A. 1974. Etho-ecologicalstudies of teal NILSSON,L. 1970. Food-seekingactivity of south wintering in the Camargue(Rhone Delta, France). Swedish diving ducks in the non-breeding sea- Wildfowl 25:123-133. son. Oikos 21:145-154. TAMISIER,A. 1976. Diurnal activitiesof Green-winged OWEN,M., AND C. J. CADI•UIt¾.1975. The ecology Teal and Pintail wintering in Louisiana.Wild- and mortality of swansat OuseWashes, England. fowl 27:19-32. Wildfowl 26:31-42. THOMPSON, S.C., AND D. G. RAVELING. 1987. Incu- OWEN, M., AND J. K•AR. 1972. Food and feeding bationbehavior of EmperorGeese compared with habits.Pages 58-77 in The swans(P. Scott,Ed.). other geese:Interactions of predation,body size, Houghton Mifflin Co., Boston. and energetics.Auk 104:707-716. PAULUS,S.L. 1984. Activity budgetsof nonbreeding YDENBERG,R. C., H. H. TH. PRINS, AND J. VAN DIJK. Gadwallsin Louisiana.J. Wildl. Manage.48:371- 1984. A lunar rhythm in the nocturnalforaging 380. activitiesof wintering BarnacleGeese. Wildfowl PAULUS,S. L. 1988. Time-activity budgetsof non- 35:93-96. breeding Anatidae:A review. Pages135-152 in ZAR,J.H. 1984. Biostatisticalanalysis, 2nd ed. Pren- Waterfowl in winter (M. W. Weller, Ed.). Univ. tice-Hall, EnglewoodCliffs, New Jersey. Minnesota Press,Minneapolis. PEDItOLI,J. 1982. Activity and time-budgetof Tufted Received21 February1992, accepted 25 November1992.

The Auk 111(4):1018-1022, 1994

Patternsof Genetic Polymorphismin Five Speciesof Penguins

NINA N. THUMSERAND JEFFREYD. KARRON Departmentof BiologicalSciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA

Conservation programs benefit from increased guins are quite abundant in captivity, making this knowledge of the basicbiology and systematicsof group well-suited for geneticand behavioralstudies. endangeredspecies (Haig et al. 1990).This study fo- In addition to facilitating penguin research,captiv- cuseson relationshipsin the genusSpheniscus, which ity has led to mixed-speciesexhibits and interbreed- includes: JackassPenguin (S. demersus),Galapagos ing between Spheniscusspecies. Fertile hybrids be- Penguin (S. mendiculus),Humboldt Penguin (S. hum- tween Jackassand Humboldt penguinsand between boldti),and MagellanicPenguin (S. magellanicus).The Humboldt and Magellanic penguinshave been re- first three taxa are considered threatened or endan- ported in captivity (Conway 1965, Araya 1983). This gered (U.S. Fish and Wildlife Service 1990, 1993). raisesquestions concerning the speciesstatus of mem- However, Jackass,Humboldt, and Magellanic pen- bers of this group. The Galapagosand Jackasspen-